(1) Field of the Invention
This invention relates to tooth inserts for use in a toothed blade and particularly its use in a slasher for paper pulp manufacture. The invention has as its main objective an insertable tooth having a greatly extended life time thereby permitting continuous use of toothed saws incorporating such an insertable tooth without the necessity of daily maintenance as is the standard practice with insertable teeth of the prior art.
2. Description of the Prior Art
Insertable teeth of the prior art used for cutting wood were generally elongated plate-like members of tool steel set in the periphery of and radially extending outward from a disc-shaped carrier which was adapted to be rotated about an axis perpendicular to the center of the disc. The insertable teeth were typically beveled to form a cutting edge in one plane, the teeth being alternately arranged and slightly offset so as to cut a kerf somewhat wider than the thickness of the plate steel actually forming each insertable tooth. The offset arrangement of each tooth was established by the presence of grooves on the leading and following edge of each insert coacting with beveled members adapted to extend into the groove, the beveled members being present in slots in the disc-shaped carrier adapted to receive the insertable teeth. One or more aperatures was typically provided for the insertion of rivets to hold the inserted teeth in place in the disc carrier. Examples of insertable teeth of the prior art are to be found in U.S. Pat. Nos. 560,426; 1,095,833; 1,141,063; 2,160,525; and 3,885,488.
As saws having insertable teeth of this type have been used as a slasher for paper pulp manufacture, it has been commonly experienced that the insertable teeth become sufficiently dull within four to eight hours use that the whole slasher blade must be removed and either new insertable teeth inserted or the old insertable teeth removed, sharpened, and then reinserted. While the cost of each insertable tooth is not large (typically less than $3.00) the amount of human labor involved in installing a complete set of insertable teeth in a slasher blade is considerable, the total upkeep costs ranging in the neighborhood of $1000 per day for each operating slasher. The high maintenance costs has heretofore prevented the general acceptance of the slasher blades using insertable teeth of this type. Further, slashers using insertable teeth of the prior art have been subject to considerable down time since the blade must be replaced every eight hours and is more typically replaced every four hours so as to achieve optimum performance.
Unlike the prior art, a slasher incorporating insertable teeth according to this invention, has been used continuously for periods of up to sixty days with no noticeable decline in performance. While the cost of producing each insertable tooth according to this invention is considerably more than in the prior art, typically three or four times the prior art cost, the extended life of the teeth and the concomitant savings experienced from significantly reduced down time and upkeep result in an overall lowering of costs for the operation and maintenance of a slasher of this type. While heretofore significant heat problems due to friction have been experienced in slashers of this type resulting in the burning or charring of wood surfaces thus rendering the wood unsuitable for paper pulp manufacture, the use of a blade according to this invention presents little or no frictional heat problem, thus significantly improving the output product of the paper pulp slasher.